Generally, rolling bearings are used in rotary portions of automobiles' transmissions, differentials, constant velocity joints, propeller shafts, turbochargers, hubs, etc., or in rotary portions of machine tools, wind power generators, etc. Such rolling bearings include an inner race; an outer race disposed radially outwardly of, and coaxially with, the inner race; and a plurality of rolling elements disposed in the annular space defined between the inner race and the outer race.
Such a rolling bearing in an automotive transmission or an automotive differential is used in an environment where there is lubricating oil, and the lubricating oil frequently contains foreign matter such as gear wear dust. If such gear wear dust enters the bearing, the bearing may break at an early stage.
In order to prevent the entry of foreign matter such as gear wear dust, sealed bearings (as disclosed in Japanese Unexamined Patent Application Publication No. 2002-327761) are generally used as rolling bearings in an automotive transmission, an automotive differential, etc. Such a sealed bearing includes annular seal members closing the openings of the annular space defined between the inner and outer races at the respective ends of the annular space. Each annular seal member includes a seal lip made of rubber, and generally kept in sliding contact with the outer periphery of the inner race over the entire circumference thereof.